1) 79 Organ Chorales, Op. 28 by Marcel Dupre. One of the most famous organists of the 20th century, the French composer Marcel Dupre intended this collection to be an introduction to the organ chorale preludes of Bach. They are fully edited by the composer, with complete fingering, pedaling, registration, articulation, and phrasing. Dupre also provides a very systematic way of learning and memorizing these short pieces. The harmonic language of these works is not dissonant but in the style of common practice period.
2) 24 Pieces for Organ or Harmonium (1933-39) by Jean Langlais. One of the most prolific French composers, the blind organist Jean Langlais wrote this collection with the intend to be performed on the organ or harmonium. Therefore, these pieces will sound equally well on the organ with or without pedals. Langlais musical style is highly modal and very colorful. In this collection you will find preludes, fugues, chorales, scherzos, and other character pieces and as well as a very easy toccata.
3) Organ Book (1956) by Jean Langlais. This collection contains 10 pieces: Prlude, Pastoral song, Choral in E minor, Flutes, Musette, Choral in F major, Scherzando, Andantino, Epithalamium, and Pasticcio. In every piece you will find the notorious sign of Langlais musical style - the use of modal system.
4) 12 Small Pieces for Organ or Harmonium (1962) by Jean Langlais. The 10 short pieces in this collection are composed in 8 church modes and 2 are written in a medieval style. They can be performed on organs with or without pedals equally well. The music shows how modern can sound a piece even if it has no key signatures at all. Perfect for creative service playing.
5) Organ Book (Parts I-III) by Ned Rorem. Ned Rorem is a famous American contemporary composer and Pulitzer Prize winner (in 1976 for his orchestral suite "Air Music"). He has been called by Time magazine "the world's best composer of art songs." He has championed tonality throughout his career in his lyrical yet forthright music.
Rorem's Organ Book contains 16 pieces which are all accessible to organists with limited technical capabilities. Part I: Fantasy, Episode, Song, Serenade, and Reveill. Part II: Rex Tremendae, Magnificat, Pie Jesu, Stabat Mataer, "Eli, Eli lama sabachthani?", and In nominae Domine. Part III: Fanfare, Fugue, Impromptu, Passacaglia, and Rondo.
If you like modal and tonal writing and mild dissonances, you will likely enjoy these collections. Each of them is easy enough to learn if you have only modest organ skills. In fact, they will serve as a great introduction to the larger pieces of the above composers and to the 20th century musical style in general.
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